1. Field of the Invention
The present invention relates to an information recording-reproducing apparatus which effects any one of recording of information on an information recording medium and reproduction of the information from the information recording medium by a head while relatively moving a carriage, on which the information recording medium has been mounted and the head.
2. Related Background Art
There have heretofore been a magnetic system and an optical system as conventional recording systems for information recording mediums. The information recording mediums are in the form of a tape, disk, card or the like. These recording systems and medium forms are properly used according to purpose. Magnetic cards of the magnetic system, which are information recording mediums in the form of a card, are excellent in ease of putting away and portability and are hence widely used in card systems such as cash dispensers.
In recent years, the quantity of information operated by the card systems has increased by the influence of an information-oriented age, and so it has been difficult to cope with such increase in quantity of information by magnetic cards. In addition, the magnetic cards are often forged and hence offer a great social problem. There is thus a demand for development of an information recording medium high in safety.
In view of the foregoing circumstances, attention is paid to an optical card which is an information recording medium of the optical system in the form of a card. The optical card has such merits as it has a capacity as large as several M bits, and is easy to mass produce and cheap. In addition, the optical card is of an additionally writing type and is hence incapable of rewriting information, thereby making forgery difficult and leaving histories. The optical card is an information recording medium high in safety even from these points of view.
An example of such a conventional optical card is illustrated in FIG. 1. FIG. 1 is a plan view of optical card C. The external shape of optical card C is rectangular. n (n being an integer of 2 or greater) information tracks 10.sub.1, 10.sub.2, 10.sub.3, . . . , 10.sub.n-1, 10.sub.n are arranged at intervals of several microns in parallel with one another in a direction parallel to the longer sides of optical card C.
An information recording-reproducing apparatus used for such an optical card is so designed that a light spot several .mu.m in diameter is formed by a light beam between the information tracks of the optical card to record or reproduce information. The information recording-reproducing apparatus is also so designed that the optical card and an optical head are driven in directions perpendicular to each other to scan the optical card while causing the light beam to follow the information track in parallel.
As illustrated in, for example, FIG. 2, an opening 2 for taking an optical card C in and out is provided in a casing 1 of the conventional information recording-reproducing apparatus, and a carriage 3 mounting optical card C thereon is movably installed in the interior of casing 1. A pair of rollers 4 for taking optical card C on and out of carriage 3 is provided between opening 2 and carriage 3. The pair of rollers 4 is driven by a driving motor (not illustrated) and feeds optical card C, being held therebetween. An optical head 5, in which an optical pickup (not illustrated) has been installed, is provided above carriage 3. Optical head 5 serves to focus a laser beam on optical card C to record or reproduce information.
Optical card C is flatly held on carriage 3 to position and align it on carriage 3 in such a manner that the direction of the information tracks of optical card C accurately coincides with the moving direction of carriage 3. Carriage 3 is provided so as to permit its reciprocative rectilinear movement in the direction of the information tracks of optical card C, and optical head 5 is provided so as to permit its reciprocative rectilinear movement in a direction perpendicular to the direction of the information tracks of optical card C. Carriage 3 is driven by a driving mechanism comprised of a belt 6, pulleys 7a and 7b, a driving motor (not illustrated), etc., and optical head 5 is also driven by a driving mechanism (not illustrated). The moving range of carriage 3 is determined by a light-screening plate 8 provided on the lower surface of carriage 3 and optical sensors 9a and 9b provided on the base of casing 1.
Incidentally, in the above-described information recording-reproducing apparatus, carriage 3 is moved in the direction of the information tracks of optical card C, and optical head 5 is moved in the direction perpendicular to the information tracks of optical card C. However, there is also known an information recording-reproducing apparatus in which carriage 3 is moved in a direction perpendicular to the information tracks of optical card C, and optical head 5 is moved in the direction of the information tracks of optical card C.
On the other hand, with the development of digital communication techniques and the servicing of communication networks in recent years, information apparatus called mobile equipment are positively used not only indoors but also outdoors. From such a point of view, the above-described information recording-reproducing apparatus is also required to make it possible to be positively used outdoors for making the best use of the excellent portability of optical card C. Therefore, it is desirable that the information recording-reproducing apparatus be made small in size and light in weight to improve its portability and can be held in one hand so as to be easily operated.
In the conventional information recording-reproducing apparatus, however, carriage 3 and optical head 5 are relatively moved, and so the center of gravity of the apparatus comes to move repeatedly. Therefore, when an operator holds the apparatus in his hand to operate it, the operability and stability thereof become poor, and the apparatus may fall from the hand to break down in the worst case. In this case, if the mass of the apparatus may be reduced to, for example, about 100 g, the influence by the movement of the center of gravity is lightened to prevent the operability and stability from being deteriorated. It is however difficult under circumstances to actually reduce the mass of the apparatus to lighter than 300 g.
In order to improve such a problem, it is considered to join a balance weight, which has the same mass as carriage 3 or optical head 5 and interlocks in an opposite direction, to carriage 3 or optical head 5. However, in this case, the driving motor for driving carriage 3 or optical head 5 comes to drive the balance weight as well, and so it is necessary to make the driving motor larger. Accordingly, a new mass of the balance weight and moreover an increased mass by the enlargement in size of the driving motor are added to the mass of the apparatus. It is hence expected that the mass and size of the apparatus are increased to impair the portability thereof.